Reference: Fataawa Ramadhaan – Volume 2, Page 543, Fatwa No.524
Fataawa as-Siyaam libni Jibreen – Page 46
Question: Is it permissible for a cook to taste the food whilst fasting?
Response: There is no problem with tasting food out of necessity and this is done by placing it on the tip of the tongue to see how sweet or sour it is. However, nothing of it should be swallowed, rather, it should be spat out or taken out of the mouth and with that the fast is not nullified [according to the preferred opinion].
And Allaah [alone] has the Complete knowledge [of all affairs].